Microsatellite DNA variation reveals high gene flow and panmictic populations in the Adriatic shared stocks of the European squid and cuttlefish (Cephalopoda)

Abstract

5 FAO-AdriaMed, Termoli (CB), ItalyIn the semienclosed Adriatic Sea, the shared stocks of the cephalopods Loligo vulgaris and Sepia officinalis represent important marine fisheries resources exploited by all coastal countries. The improving of knowledge on the demographic features of these shared stocks is internationally relevant for adopting responsible management and conservation of these marine resources. Analyses of microsatellite variation in geographical samples collected from all parts of the Adriatic Sea were performed using arrays of species-specific dinucleotide and tri-nucleotide loci. In L. vulgaris the level of genetic variability was consistent with that observed in other loliginid species, whereas the S. officinalis stock showed a microsatellite variation markedly lower than that estimated for the Atlantic and Mediterranean populations collected around the Iberian peninsula. The weak spatial genetic differentiation, the discordant results of the genetic divergence estimators and the lack of any geographical cline in the spatial genetic differences suggest the occurrence of single genetically homogeneous populations within the Adriatic stocks of both species, recommending a coordinated management of the squid and cuttlefish by the Adriatic fishing countries. On the contrary, significant differences detected in temporal replicates of S. officinalis might suggest that allelic frequency can change relating to reproductive behaviour.

Microsatellite DNA variation indicates low levels of genetic differentiation among cuttlefish (Sepia officinalis L.) populations in the English Channel and the Bay of Biscay

“…When loci Sof3 and Sof5 were excluded for the three northern sampling sites of the present study, a rather low mean number of alleles (N a = 6.9) was found that was comparable to the findings of Garoia et al (2004), who reported a mean number of 6.4 alleles per locus for the panmictic Adriatic cuttlefish.…”

“…Locus Sof3 has been reported to display two parallel arrays of alleles differing by one base pair (Shaw and Pérez-Losada, 1999) and was omitted in the study of Garoia et al (2004). A biallelic character of Sof3 was also revealed in the current study; therefore, the sequences of several Sof3 clones were determined to reveal the nature of the differences prior to adjustment and binning of the two arrays (cf.…”

“…A certain degree of statistical linkage between the three loci was previously suggested by Pérez-Losada et al (2002) for S. officinalis samples around the Iberian Peninsula. Garoia et al (2004) excluded locus Sof5 (and Sof3) from their study and reported no significant linkage disequilibrium between any pairs of the remaining five loci.…”

“…Along the Iberian Atlantic and Mediterranean coast, microsatellite analysis revealed significant population subdivision (Pérez-Losada et al, 2002). By contrast, in the semi-enclosed Adriatic Sea, S. officinalis lives in a panmictic population (Garoia et al, 2004). No verified genetic information existed for the northern distribution range of this species (Denis and Robin, 2001), which extends through the Bay of Biscay and the English Channel into the North Sea.…”

“…Garoia et al (2004) performed allele size permutation tests and also concluded that F ST is the more appropriate estimator for weak population structures as seen for S. officinalis in the Adriatic Sea. This is also the case in the present study; we will therefore present both F ST and R ST in Results, but only discuss the F ST indices.…”